The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory captions and links exemplifying features within the Earth system. The community is invited to contribute digital imagery, short captions and relevant links.

Armed Intrusions

The photo above showing what looks like a huge fossilized spider or a giant octopus was photographed on Februaty 11, 2006 at Soldier Canyon, near Tucson, Arizona. This curious rock formation is likely partially composed of gneiss (metamorphic rock). The "arms" that protrude from the rock surfaces are actually dikes -- intrusions of harder rock eroding at a slower pace than the host rock formation.